20121216.1754

I built a wonderful 12 TB RAID 50 NAS and it runs smooth and quiet, but consumes around 70 watts under load, which is still good for 6 Hitachi enterprise class drives. So I thought about sending these 6 drives to standby after 1 hour of silence on their bus:

First install hdparm and set up the config-file ( we are on Debian Squeeze as root here ):

Looks good so far, but after 3 hours of inactivity the drives are still active. Reducing the value to 240 ( 20 minutes ) works great, so whats wrong here?

Stopping all services and testing them one by one reveals, that smartd causes the drives to stay awake.

I edited /etc/smartd.conf to contain "-n standby":

DEVICESCAN -n standby ...

That should prevent spinning discs up when they are in standby - but that did not solve the problem, because the drives were not spun down when smartd checked them, so it accessed them and the spindown timer was reseted.

In addition to the "-n standby" option I had to increase the check-interval in /etc/default/smartmontools to something slightly above my spindown timer:

Now all 6 drives fall asleep after one hour saving me around 40 watts. My OS is installed on a separate SSD, so the drives only wake up when the NAS serves data, or backs up my servers. S.M.A.R.T.-checks are executed less often, but that should be no problem.

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